I'm unable to register my Mac Mini (Late 2012). Says serial is invalid.

I'm trying to register my Mac Mini (late 2012) so I can get support for another issue with it. I grabbed my serial from the "About This Mac" window, and attempt to register using that. However, I get an error saying "We're sorry, but this serial number is either invalid or it is for Apple software or accessories. If you are trying to register Apple hardware other than an accessory, please check your information and try again."

I'm also unable to update Mountain Lion from 10.8.1 to 10.8.2. It just takes me to the App Store update screen, but not OS update appears.